如何匹配str_replace_all的起始字符和结束字符

#include <regex>
#include <string>

std::string str_replace_all(std::string str, std::string start_char, std::string end_char, std::string replacement) {
    std::regex pattern(start_char + "(.*?)" + end_char);
    return std::regex_replace(str, pattern, replacement);
}

int main() {
    std::string str = "This is a test string. [replace_this] [replace_that]";

    std::string result = str_replace_all(str, "\\[", "\\]", "REPLACED");

    return 0;
}

#include <algorithm>
#include <string>

std::string str_replace_all(std::string str, std::string start_char, std::string end_char, std::string replacement) {
    size_t start_pos = 0;
    while ((start_pos = str.find(start_char, start_pos)) != std::string::npos) {
        size_t end_pos = str.find(end_char, start_pos + start_char.length());
        if (end_pos == std::string::npos)
            break;
        str.replace(start_pos, end_pos - start_pos + end_char.length(), replacement);
        start_pos += replacement.length();
    }
    return str;
}

int main() {
    std::string str = "This is a test string. [replace_this] [replace_that]";

    std::string result = str_replace_all(str, "[", "]", "REPLACED");

    return 0;
}